CarbonSteel
Well-Known Member
This all day. I recently moved to Colorado and the 4.88's are not cutting it with the now absolutely gutless 3.6L.
I am actually considering re-gearing to 5.38's...somebody talk me out of this...
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3.6L, 8 AT, 37”: 4.88 or 5.13?
- Thread starter Chocolate Thunder
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I am actually considering re-gearing to 5.38's...somebody talk me out of this...
CarbonSteel
Well-Known Member
Go 5.13 and don't look back. I went 4.88 and it was "ok" at sea level but not at this altitude. When I had 35's and 4.88 it was perfect and torquey so 5.13 would be a good match.
DesertsJL
Well-Known Member
Bit of a revival to this thread.
On my 2018 JLRU I went with 5.38 gears. Initially with 35’s and later with 37’s. I LOVED them. The 8th gear is so tall that it never felt strung out, ever. It was a dream to drive. If there was any concern it was that the 5.38 gears wouldn’t be as robust as a lower gear set, however it never caused me issue, though I’m not much for bouncing on rocks.
On my 2018 JLRU I went with 5.38 gears. Initially with 35’s and later with 37’s. I LOVED them. The 8th gear is so tall that it never felt strung out, ever. It was a dream to drive. If there was any concern it was that the 5.38 gears wouldn’t be as robust as a lower gear set, however it never caused me issue, though I’m not much for bouncing on rocks.
JeepinJason33
Well-Known Member
I am about 5,000 miles and 15-20 trail runs into my 5.13's on 37's with 3.6L and zero problems up here in Denver... Very glad I went with them over the 4.88's. When I was trying to decide early this year, there were more people pushing for 4.88's, seems like more and more are now going with 5.13s.
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P&PJeep
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What RPM are you turning at 75 mph? The more I read about the the more I bounce between 4.88 & 5.13
Coolbaldguy
Well-Known Member
As I write this I realize that there are a lot of threads about this topic, but this thread has stayed on topic and people with real world experiences are sharing their opinions. Everyone has unique needs and expectations, so I will share mine and hopefully it will help to get valuable opinions. I have a 2 door so it is lighter weight than most. I do have a heavy wheel tire combo ( 134#). My jeep is not a daily driver but I live in rural are that requires highway speeds to get anywhere. My thoughts are that I have run the stock 4:11 ratio for 5000 miles and it is not terrible, but I am looking forward to a gear change. Maybe 4:88 would be enough and have stronger pinion than 5:13? Or will I wish I had 5:13 except when I need to travel 75+ mph? I am not a speed demon, but I also need to stay out of the way of interstate traffic that tends to run 80ish mph around here. The short wheelbase of a 2 door on 37” tires can be a bit “twitchy” above 75 mph.
DesertsJL
Well-Known Member
It's not about top speed. It's about using the vehicle's full range. My perspective....if I have 8 gears I want to use them all. If my top speed is going to be 70, then I should be able to use 8th gear comfortably at 70mph and not feel that the Jeep is wanting to hunt gears. I opted to go with a 5.38 gear because I live in a mountainous area and I went with 37's. At highway speeds the Jeep was able to pull grade, yet never felt wound up. At 70mph I was turning 2,300rpm and at 80mph I was only turning 2,600rpm both with very light throttle. The only drawback that I felt that the 5.38 gears gave me was a smaller pinion gear, but honestly, unless you are beating on it, the pinion gears on the JL's are much beefier and have been holding up well.
jdhunt0
Well-Known Member
I have a JLUS running 35s right now. Leaning towards 37s next. The Jeep is my daily driver. I have debated what gears for a while and finally placed my order last night. Going with 4.88. Hopefully I don’t regret it.
DanW
Well-Known Member
If going to 37's I think you'll hit the bullseye with 4.88's. But some have gone with 4.88's and 35's and love it. For me, the rpms would be a bit too high at 75mph, but everyone has their own comfort level with that.
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JeepinJason33
Well-Known Member
Around 2,500-2,600. Just tried it on a flat spot yesterday. But keep in mind this is at 6,000' with a 6,000 pound JLUR
Gadgettr1
Well-Known Member
What gear is that in? I run 1950rpms (just under 2 on the needle) at 75mph in 8th gear, and 2450rpms at 75mp in 7th gear. V6 with 315's (Ridge Grapplers on Mopar simulated beadlocks.
JeepinJason33
Well-Known Member
8th gear. I ran 2,300-2,400 before the gear change so only about 100 rpm on the same stretch of highway at the same speed. Keep in mind, heavy Jeep and at altitude. I am sure the RPM's would be lower at sea level.
Gadgettr1
Well-Known Member
I've never weighed my Jeep but, she's not light by any means lol. And yes, I'm right at sea level here on the coast, great info. Thank you.
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